1. Field of the Invention
The present invention relates to a skin fluorometer perfusion monitor and more specifically to a hand held skin fluorometer to measure blood perfusion at a position exterior to the skin tissue.
2. Description of the Prior Art
It is often desirable to provide for a measurement of the perfusion of body tissue by the blood. Such a measurement is useful, for example, to determine if a portion of the body is receiving an adequate supply of blood such as after a surgical procedure. For example, it would be desirable to monitor the perfusion in a body extremity, such as a finger or hand, which was either partially or completely severed and then reattached. The measurement of blood perfusion is important so as to determine the likelihood of the reattached member receiving an adequate blood supply to insure a healthy healing of the reattached member. Another area in which the monitoring of the perfusion of blood is useful is when skin flaps have been attached such as for burn victims.
One method of measuring the blood perfusion is to measure the level of fluorescense of a fluorescent dye, such as fluorescein, which is carried by the bloodstream and diffuses into particular body tissue through the blood perfusion into the tissue. The fluorescent dye may be injected into the bloodstream and with the level of fluorescense at some later time measured at the particular tissue area. The crudest way of injecting the dye into the bloodstream is to ingest the dye but this takes a considerable time before the dye ultimately get into the blood.
A more common method is to inject the dye directly into the bloodstream and then wait for about fifteen (15) minutes for the dye to diffuse into the tissue of interest. A measurement of the fluorescense of the tissue of interest, such as a reattached finger, is then made and with a comparison made between the fluorescence at the reattached finger and at a normal finger. It would be useful to make this measurement on a regular periodic basis, such as every hour, so that if a blockage of either the artery or vein to the reattached area occurs, the blockage can be detected within a short time and surgery can be performed to cure the blockage before the reattached area dies because of a lack of blood supply.
The general methods of measuring this perfusion into the blood tissue, using fluorescense, has been of two (2) types. First, the intensity of the fluorescense may be measured directly with the eyes but such a qualitative measurement requires large doses of fluorescent dye and such large doses cannot be repeated on a periodic regular basis such as every hour.
Another method of measuring uses a fluorometer which has a long optical fiber bundle and with this bundle carrying blue exciting light to the skin through a first group of fibers in the bundle and with a detection of the fluorescense with the remaining group of fibers in the bundle. The prior art fluorometer normally includes a high intensity steady state light source such as a one hundred fifty (150) watt tungsten halogen light and with this light filtered with a blue filter to give blue exciting light. The fluorescent light is collected by the remaining fibers in the group and is filtered by a yellow-green filter. The light energy passed by the yellow-green filter is directed to a photomultiplier so as to provide a measurement of the collected fluorescent light energy.
The above described type of prior art device is relatively large, expensive and is sensitive to ambient light. In particular, sensitivity to ambient light is so critical that the device usually includes a shield so as to prevent the entry of any ambient light into the device when making the measurement of fluorescense. As an alternative, the measurement may be made in a dark room but such a measurement in a dark room is obviously difficult to perform.